So currently i run a ReadyNAS 104 with 4 x 4TB WD Red drives in it and they're nearly full. To increase my storage is it as simple as buying a 12TB WD Red and just swapping it in place of one of the 4TB ones? From what i've read i do this while it's still turned on and it should just adjust itself to the new storage?
Assuming you are using XRAID/RAID5, you'll have to replace two drive to get a size increase. Yes, you swap them out with power on. The first one will just re-sync the existing volume size. The second one will first re-sync that, then sync a second layer with the first larger drive, which will add to the available space.
